It is generally known, in order to reduce the pollutant emissions, to treat the exhaust gases of a combustion engine, for example of an Otto or diesel engine, by an exhaust-gas treatment device arranged in the exhaust tract. Here, the efficiency of the exhaust-gas aftertreatment device is influenced very decisively by the temperature prevailing in the exhaust-gas aftertreatment device and by the fuel/air ratio used during the combustion in the combustion engine. In order, for example, to realize adequate conversion performance of the exhaust-gas aftertreatment device, a certain operating temperature, the so-called light-off temperature, may be attained, which may be 120° C. to 250° C.
In motor vehicles driven by Otto or diesel engines, it is, for example, conventional to control the temperature of the exhaust-gas aftertreatment device so as to ensure a fast light-off of the catalytic converter, for example in the case of an Otto engine, by temporarily setting a late ignition angle, as a result of which the combustion is shifted partially into the outlet tract and the exhaust-gas temperature during the warm-up phase is increased. In the case of diesel engines, it is inter alia conventional, for example in order to assist the regeneration of soot filters, to increase the exhaust-gas temperature from time to time by intake air throttling and/or intake air pre-heating and/or by a late start of injection and/or post injection.
Likewise, in the case of motor vehicles with a so-called automatic start-stop facility, a control regime is known which helps to prevent the temperature of the exhaust-gas aftertreatment device from falling below a certain limit value, for example the light-off temperature, during a temporary stop phase. For example, EP 0 989 299 B1 discloses a control device for a motor vehicle engine, which control device is configured so as to change the state of the motor vehicle engine automatically between a stopped state and an operating state on the basis of a predetermined condition. In particular, the described control device is capable of preventing an engagement shock of a frictional engagement or clutch device by engine torque control at the time of start-up of the vehicle, even if the engine torque control is not possible. To determine whether or not engine torque control can be carried out, it is proposed inter alia that the temperature of a catalytic converter be determined, and that a torque reduction not be carried out if said temperature is lower than a certain value.
In particular during operation of a combustion engine in the low-load range, for example at an engine output power of less than approximately 20 Nm or when the engine is being used as an engine brake, the stability of the combustion is a problem which cannot be disregarded with regard to a post-injection calibration. Furthermore, at a relatively low combustion pressure within the respective engine cylinder, there is an increased tendency for the fuel injected into the cylinder to precipitate on the cylinder interior walls. This leads to excessive contamination of the engine oil. Furthermore, the attainment of high exhaust-gas temperatures, for example for the regeneration of soot filters, is particularly difficult in the low-load range in particular in the case of diesel engines on account of the combustion thereof, which is already lean out of principle.
The inventors have recognized the above issues and provide a solution herein to at least partly address them. A method for controlling an exhaust-gas aftertreatment device of a vehicle hybrid drive is provided. The method comprises operating the hybrid drive only by a combustion engine, only by a non-combustion motor, or by both, as a function of a temperature of the exhaust aftertreatment device, and conducting exhaust gas of the hybrid drive at least partially through the exhaust aftertreatment device, the engine and motor each providing output to power the vehicle.
In this way, the temperature of the aftertreatment device may be controlled by controlling the extent to which the exhaust gases produced by the engine are conducted through the device. For example, if the exhaust temperature is greater than the temperature of the device and the device is currently operating at a temperature lower than desired, the hybrid drive may be operated by only the engine in order to quickly heat up the device. Thus, this permits optimum operation of the exhaust-gas aftertreatment device in particular with regard to exhaust-gas purification or conversion performance.
It is pointed out that the features specified individually in the patent claims may be combined with one another in any desired technologically meaningful way and discloses further embodiments of the present disclosure. The description, in particular in conjunction with the figures, characterizes and specifies the disclosure further.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.